JP2002043721A - Method and device for inspecting printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable performing inspection of a printed board that dispenses with many contacts or access pins, and that does not requires preparation of inspection boards corresponding to each kind of board. SOLUTION: A board 10 to be inspected is pressure-welded on an inspection board 1 that plural contacts 6 is arranged in a matrix through a conductive sheet 2. Direct current is applied to both ends of the pressure-welded sheet from DC power supply. Then, voltage of the each contact 6 is detected, and the normal/defective condition of the board 10 is decided on the basis of distribution of the detected voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting a printed circuit board for electrically inspecting whether a conductor circuit, a resist or the like of the printed circuit board is correctly formed.

[0002]

2. Description of the Related Art In recent years, with the demand for higher density printed circuit boards, thinner conductor circuits by increasing the number of layers, and the reliability of through holes, the limit of visual inspection has arisen. Wiring inspection system has come to be used as a typical inspection method.

In this wiring inspection system, a substrate to be inspected is placed on an inspection board called a fixture having electrical access pins, and a constant voltage is applied between lands of a wiring pattern of the substrate to be inspected to obtain a “conduction”. Insulation state "is determined by a resistance value, and the presence or absence of" disconnection or short circuit "is inspected.

[0004] Therefore, a fixture includes a dedicated type in which pins are arranged in accordance with a wiring pattern of a substrate to be inspected,
There is a universal type in which necessary pins are selected from a large number of pins arranged on a board in advance according to a wiring pattern of a substrate to be inspected and inspected.

[0005]

However, in the above-mentioned dedicated type, a fixture must be prepared for each type of a board to be inspected, so that it takes time and cost to prepare a fixture corresponding to a new board. Take it.

On the other hand, the universal type can solve the problem of the exclusive type because necessary pins can be selected from a large number of pins according to the wiring pattern of the substrate to be inspected.
In order to test a 00 mm square board at a time, about 40,000 access pins are required, and software for collecting data from the access pins is also required, which increases the cost and increases the cost. Takes time.

An object of the present invention is to make it possible to inspect a substrate without requiring a large number of access pins and without preparing a fixture corresponding to each type of substrate.

[0008]

In order to solve the above-mentioned problems, according to the present invention, a conductive sheet is formed by placing a substrate to be inspected with a pattern surface downward on a plate surface of an inspection board in which a plurality of contacts are arranged in a matrix. And applying a DC voltage between both ends of the pressed sheet or between the patterns of the substrate to be inspected to detect the voltage of each contact, and determine the quality of the substrate to be inspected based on the detected voltage distribution. It was adopted.

By employing such a method, the resistance of the pattern portion of the substrate to be measured which is pressed against the conductive sheet is extremely lower than that of the conductive sheet. Therefore, a current flows on the pattern side in a portion where the sheet is in contact with the pattern, and a current flows on the sheet side in a portion where the pattern is not in contact with the sheet. Therefore, when a voltage is applied from one side of the conductive sheet to the other or between the patterns on the substrate to be inspected, a specific voltage distribution is generated on the conductive sheet that is correlated with the pattern on the printed board. The voltage distribution is detected by the contact.

At this time, for example, if a voltage distribution of a non-defective product serving as a reference substrate is taken in advance and compared with the distribution of the substrate to be measured, pass / fail can be determined from the difference.

Further, at this time, when the voltage application position is changed, the current path changes, so that the state of the voltage distribution also changes. However, since the failure location does not change, if a large number of paths are taken,
It is also possible to pinpoint the failure location.

At this time, the plate surface of the inspection board, on which a plurality of contacts are arranged in a matrix, is pressed against the pattern surface of the substrate to be inspected via a conductive sheet, and both ends of the pressed sheet or both ends of the substrate to be inspected are pressed. A method of applying a DC voltage between patterns to detect the voltage of each of the contacts, and determining the quality of the substrate to be inspected based on the detected voltage distribution can also be adopted.

By employing such a method, the voltage distribution can be detected by pressing the conductive sheet and the inspection board against the substrate to be inspected, so that the conductive sheet and the inspection board can be arbitrarily placed on the substrate to be inspected. It is possible to detect the voltage distribution at the location by pressing against the location.

An inspection board in which a plurality of contacts are formed in a matrix on a plate surface, a conductive sheet interposed between pattern surfaces of a substrate to be inspected which are pressed against the contacts of the inspection board, and both ends of the conductive sheet or the conductive sheet. It is possible to employ a configuration including a DC power supply that applies a DC voltage between the patterns of the inspection substrate, and a determination unit that detects a detection voltage of each of the contacts and determines the acceptability of the inspection target substrate from the detected voltage pattern. .

By adopting such a configuration, when pressure is applied to the substrate to be inspected, the pattern of the substrate to be inspected comes into close contact with the contact of the inspection board via the conductive sheet. In this state, when a DC voltage is applied between both ends of the conductive sheet or between the patterns on the substrate to be inspected, a voltage distribution is generated on the conductive sheet that is correlated with the pattern on the printed circuit board. Pass / fail can be determined by the determination means.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment.

The inspection apparatus of this embodiment comprises an inspection board 1, a conductive sheet 2, a pressure contact plate 3, a DC power supply 4, and a judging means 5.

The inspection board 1 is provided with a plurality of contacts 6 made of a conductor such as a metal on the plate surface, and the contacts 6 are arranged in a matrix as shown in FIG. In the case of 50 to 60). Each contact 6 is connected to the determination means 5 as described later.

The contact 6 may be a conventional electric access pin (for example, a contact having a coil spring and a socket for accommodating the contact). By using conductive rubber or the like, a simple protrusion that does not use a spring, such as a ball grid, can be used.

The conductive sheet 2 has a sheet shape formed to cover the inspection board 1, and may be formed of, for example, a conductive film, a conductive vinyl, or the like, in addition to a conductive rubber.

Feeding points 8 and 8 'are provided at both ends of the conductive sheet 2 so that one side is positive and the other side is negative.

In this embodiment, the power feeding points 8 and 8 'are provided on the conductive sheet 2. However, in addition to this, at both ends of the inspection board 1, one side is positive and the other side is negative. It is also possible to provide the contacts 8, 8 '. If the contact points 8, 8 'are made to be in contact with the pressed conductive sheet 2 by, for example, forming a land pattern, power can be supplied to the conductive sheet 2.
8 'can be substituted.

The pressure contact plate 3 is an insulating plate formed to have a size to cover the inspection board 1. Here, an insulating plate is formed using, for example, acrylic, and a weight 9 is attached to the center of the insulating plate. A uniform load is applied to a substrate to be inspected 10 described later. The shape and material of the press contact plate 3 are not limited to the above.

The DC power supply 4 is a constant voltage power supply for supplying a voltage at which the substrate 10 to be inspected does not cause dielectric breakdown to the power feeding points 8, 8 'of the conductive sheet 2, for example, a voltage of about 5V here. is there.

The judging means 5 comprises a sampling means 11 and a computer 12.

The sampling means 11 comprises a matrix substrate 13, a switch circuit 14 for scanning, and an A / D conversion circuit 15.

The matrix substrate 13 arranges the contacts in a matrix to collect the contact output of the inspection board 1. The matrix substrate 13 is connected to the switch circuit 14. The switch circuit 14 is a scanning switch constituted by an analog switch, a mechanical relay, or the like, and sequentially scans and outputs the voltage of each contact 6 by, for example, a sweep signal from the computer 12. The output voltage is converted by the A / D conversion circuit 15 and input to the computer 12.

Here, in order to collect the output of the contact 6, the socket-shaped matrix substrate 13 is used. However, the cable may be directly wired from the contact 6 to the switch circuit 14 without using the matrix substrate 13. Good.

The computer 12 has a processing program for processing input data. For example, the computer 12 displays a voltage distribution based on the input data to notify a failure as described later.

This embodiment is configured as described above.
Hereinafter, the inspection method of the present application will be described by describing the operation of the inspection apparatus.

In this inspection apparatus, the feeding points 8, 8 'of the conductive sheet 2 and the DC power supply 4 are connected. That is, the plus output of the DC power supply 4 is connected to the plus contact 8, and the minus output of the DC power supply 4 is connected to the minus feed point 8 ′. Further, after each contact 6 of the inspection board 1 is connected to the switch circuit 14 via the matrix substrate 13, the output of the switch circuit 14 can be input to the computer 12 via the A / D conversion circuit 15.

When the inspection apparatus is set up in this way, the conductive sheet 2 is laid on the contact 6 of the inspection board 1 and the substrate 10 to be inspected is placed on the conductive sheet 2 on the contact 6 with the pattern side down. I do. Next, the press-contact plate 3 is pressed against the placed substrate to be inspected 10, and a voltage is applied from the DC power supply 4. Then, the voltage of each contact 6 is sequentially detected by scanning the switch circuit 14, and each detected voltage is converted into a digital value by the A / D conversion circuit 15 and input to the computer 12.

At this time, the substrate 1 to be inspected is
When 0 is pressed, the pattern surface of the inspection target substrate 10 is pressed against the conductive sheet 2, and the pressed conductive sheet 2 is pressed against the inspection board 1.

Since the resistance of the pattern portion of the substrate 10 to be inspected pressed against the conductive sheet 2 is extremely lower than that of the conductive sheet 2, a current is applied to the pattern side in the portion where the sheet 2 is in contact with the pattern. Flows. Meanwhile, sheet 2
However, the current flows to the sheet side in the portion not in contact with the pattern.

As a result, a voltage distribution is generated on the conductive sheet 2 that is correlated with the pattern of the substrate 10 to be inspected. Incidentally, this is also effective for a laminated substrate.

Therefore, if attention is paid to the difference between the voltage distributions, it is clear that a good product and a defective product can be easily determined in a short time.

For example, the normal voltage distribution of a good product is stored in the computer 12 by the above-described method. Next, the voltage distribution of the substrate 10 to be inspected is measured, and the measured voltage distribution and the voltage distribution of the good product are compared. By comparison, a method of determining the quality of the substrate to be inspected 10 can be performed.

Therefore, it is sufficient that the voltage distribution of the conductive sheet 2 can be detected, so that the contact 6 for each land is not required unlike the conventional universal type, and the contact according to the pattern of the substrate is different from the conventional dedicated type. Since the number of contacts 6 need not be provided, the number of contacts 6 can be reduced.

Incidentally, in this determination, each contact 6
Is plotted on the X coordinate and the Y coordinate, and the voltage distribution characteristic diagram in which the voltage values of the plot coordinates are plotted on the Z coordinate is displayed on the computer 12 so that analysis can be performed easily and in a short time. .

Therefore, in order to verify that the voltage distribution diagram is effective for the judgment, a test printed board was prepared, and the following test was performed using the board.

That is, first, the voltage distribution of the prepared substrate was measured by the above-described method. FIG. 2 shows the measurement results.
FIG. 3 shows a voltage distribution characteristic diagram based on the measurement results.

Next, as a test 1, a short-circuit portion was created by a method of covering the pattern surface of the prepared substrate with about 1/3 of the aluminum foil 16 as shown in FIG. 4, and the voltage distribution was measured. FIG. 5 shows the measurement results. FIG. 6 shows a voltage distribution diagram based on the measurement results.

When comparing FIG. 3 with FIG. 6, the voltage level of FIG. 6 is lower than that of FIG. 3, but the rate of decrease is proportional to the measured distance from the voltage application point (position 0 in the figure). Have fallen in the same way. Therefore, the difference between them is taken, and the result is shown in FIG. FIG. 8 shows a voltage distribution characteristic diagram based on the calculation results. From FIG. 8, it can be seen that the voltage has changed significantly due to the short circuit. From this result, it was proved that a failure of the substrate could be found.

Further, as a test 2, as shown in FIG. 9, a method of creating a short-circuit state by covering a part of the substrate with a ribbon-shaped aluminum foil 16 'and measuring the voltage distribution to determine the failure location Verified.

The measurement results are shown in FIGS. 10 and 11. FIG. 10 shows the measured values when there was no aluminum foil 16 ′.
1 is a measured value when the aluminum foil 16 'is covered.
FIG. 12 shows voltage distribution characteristics based on the measurement results.
FIG. FIG. 14 shows a result obtained by taking a difference between the measured values, and FIGS. 15 and 16 show voltage distribution characteristics based on the measured result. Here, FIG. 16 is obtained by rotating FIG. 15 by 90 ° about the Z axis.

As is clear from FIGS. 15 and 16, there is a point where the voltage value greatly changes. Looking at this point,
It corresponded to the position covered by the aluminum wheel 16 '. Thus, it can be seen that the failure location can be specified.

Incidentally, the voltage distribution characteristic diagram is obtained by plotting a series of rows and columns as a result of the measurement difference shown in FIG. Therefore, for example, the S3 column (1 to 1) shown in FIG.
10) and the values in the eighth row of the graph shown in FIG. 19 can be considered as a set.
5 and FIG. 16 that the position covered by the aluminum wheel 16 'can be specified.

From the above results, it can be seen that a failure of the printed circuit board can be detected. In addition, it can be seen that the failure location can be specified by Test 2.

The voltage is applied to the path indicated by reference numeral a in FIGS. 9 and 10. Therefore, if the path is changed by changing the voltage application location, the voltage distribution should also change. At this time, since the failure location does not change, it can be easily understood that the failure location can be specified more accurately by overlapping the distribution characteristics with different routes.

Next, FIG. 19 shows a second embodiment of the present invention in which the inspection board 1 and the conductive sheet 2 are miniaturized so that a failed portion of the inspection target board 10 can be specified precisely.

That is, the size of the inspection board 1 and the size of the conductive sheet 2 are formed so as to match the size of a specific range for narrowing down a failed portion. The number of contacts 6 on the inspection board 1 is determined according to the accuracy.

Each contact 6 is the same as in the first embodiment.
It is connected to a determination unit 5 composed of a sampling circuit 11 and a computer 12.

This apparatus is suitable, for example, for use in precisely identifying a failed portion of the inspection target board 10 in which the failed portion is identified in the first embodiment.

For example, the conductive sheet 2 is applied to the pattern surface of the failure location specified in the first embodiment, and the inspection board 1 is pressed. Then, the pattern surface of the substrate 10 to be inspected is pressed against the conductive sheet 2, and a DC power supply 4 is connected to both ends of the conductive sheet 2 to apply a voltage. After that, if data is sampled and processed in the same manner as in the first embodiment, a failure point can be specified. At this time, if the number of the contacts 6 is made dense, it is obvious that the failure location can be specified with higher accuracy.

On the other hand, in the above-described embodiment, an example in which a voltage is applied to the conductive sheet 2 has been described.
However, the present invention is not limited to this. For example, as shown in FIG. This is the conductive sheet 2
This is because the voltage distribution on the pattern surface of the substrate 10 to be inspected is detected and determined using the method described above, so that a voltage distribution can be obtained if a current can flow through the conductive sheet 2.

Further, since the voltage distribution is detected as described above, it is possible to detect a failure of the board to be inspected 10 on which components are mounted.

That is, by applying a voltage that does not damage components, the voltage distribution of the substrate 10 to be inspected can be detected. There is also an effect that a soldering failure can be detected at the same time.

In the embodiment, the substrate 10 to be inspected is mainly
Has been described as a single-sided substrate, but it goes without saying that a double-sided substrate is also included.

[0060]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is constructed as described above, and uses a conductive sheet to detect and determine the voltage distribution on the pattern surface of a substrate to be inspected. Inspection can be performed. In addition, since the inspection can be performed without preparing an inspection board provided with a contact for each type of substrate, the inspection can be performed inexpensively in a short time.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 Measurements of Test 1

FIG. 3 is a voltage distribution characteristic diagram of test 1.

FIG. 4 is a schematic diagram showing a measurement method of Test 1.

FIG. 5 is a measurement diagram of test 1.

FIG. 6 is a diagram showing a voltage distribution characteristic of Test 1;

FIG. 7: Measurement values of Test 1

FIG. 8 is a voltage distribution characteristic diagram of test 1.

FIG. 9 is a schematic diagram showing a measurement method of Test 2.

FIG. 10 Measurements of Test 2

FIG. 11: Measurements of Test 2

FIG. 12 is a voltage distribution characteristic diagram of Test 2

FIG. 13 is a voltage distribution characteristic diagram of Test 2;

FIG. 14: Measurement values of Test 2

FIG. 15 is a voltage distribution characteristic diagram of Test 2;

FIG. 16 is a voltage distribution characteristic diagram of Test 2

FIG. 17 is a voltage distribution diagram of test 2.

FIG. 18 is a voltage distribution diagram of Test 2

FIG. 19 is a configuration diagram of a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inspection board 2 Conductive sheet 3 Pressure contact plate 4 DC power supply 5 Judgment means 6 Contact 7 Cable 8 Contact 8 'Contact 10 Substrate to be inspected 11 Sampling means 12 Computer 15 A / D conversion circuit

Claims (3)

[Claims] An inspection board having a pattern surface facing down is pressed against a plate surface of an inspection board in which a plurality of contacts are arranged in a matrix form via a conductive sheet, and both ends of the pressed sheet or both ends of the inspection board are pressed. A method of inspecting a printed circuit board, wherein a DC voltage is applied between patterns to detect the voltage of each of the contacts, and the quality of the board to be inspected is determined based on the detected voltage distribution. 2. A plate surface of an inspection board in which a plurality of contacts are arranged in a matrix on a pattern surface of a substrate to be inspected by pressing through a conductive sheet. A method of inspecting a printed circuit board, wherein a voltage of each contact is detected by applying a DC voltage, and the quality of the board to be inspected is determined based on the detected voltage distribution. 3. A test board in which a plurality of contacts are formed in a matrix on a plate surface, a conductive sheet interposed between pattern surfaces of a test substrate to be pressed against the contacts of the test board; An inspection apparatus for a printed circuit board, comprising: a DC power supply for applying a DC voltage between patterns on an inspection board; and a determination unit for detecting a detection voltage of each of the contacts and determining whether the inspection target board is good or bad based on the detected voltage pattern.